Sectional trawl doors



Jan. 24, 1967 J.I UKE1A 3,299,560

7 SECTIONAL TRAWL' DOORS Original Filed Aug. 26, 1960 2 Sheets-Sheet 1 IN VEN TOR. FRANK vf. UL E 1'14 A T'TOE/VEVS' I Jan. 24, 1967 F. J. LUKETA 3,299,560

SECTIONAL TRAWL DOORS Original Filed Aug. 26, 1960 2 Sheets-Sheet 2 IN VEN TOR.

FRANK J MIA/57A A rive/VH6 United States Patent 3,299,560 SECTIONAL TRAWL DOORS Frank J. Luketa, 5567 Greenwood Ave., Seattle, Wash. 98103 Continuation of application Ser. No. 331,614, Dec. 18, 1963, which is a continuation of application Ser. No. 52,140, Aug. 26, 1960. This application Dec. 30, 1965, Ser. No. 524,369

6 Claims. (Cl. 43--9) This application is a continuation of my now abandoned copending application Serial No. 331,614, entitled, Multisection Trawl Door, and filed December 18, 1963, as a continuation of my now abandoned application Serial No. 52,140, filed August 26, 1960 and entitled Multisection Trawl Door. Certain features of the disclosed subject matter pertaining to trawl door constructions are to be found in now abandoned copending US. patent application Serial No. 219,276, filed August 24, 1962, and entitled Trawl Doors. Door securing stanchion means of the type alluded to herein are disclosed in my US. Patent No. 3,006,097, dated October 31, 1961, and entitled Securing Stanchion For Trawlers. Flotation means of the type mentioned herein is disclosed in my US. Patent No. 3,013,356, dated December 19, 1961, and entitled Floats For Trawl Nets. Door-connecting means are disclosed in my US. application Serial No. 508,634, filed October 22, 1965 entitled Apparatus and Method for Drum Hauling of a Large Capacity Trawl Net (a continuation of my prior now abandoned application Serial No. 294,331, filed I uly 11, 1963, and entitled Drum Hauling of a Large Capacity Trawl Net). Also, a companion US. application Serial No. 520,818, filed Dec. 16, 1965, entitled Trawl Net Load Responsive Apparatus (a continuation of my prior now abandoned application Serial No. 305,485, filed August 29, 1963, and entitled, Trawl Net Load Responsive Trawling Apparatus and Method) more fully discloses a load sensing means and trawl net rigging arrangement alluded to and partially disclosed herein.

This invention relates to improvements in trawl doors such as may be used for either midwater or bottom trawling. The invention is herein illustratively described by reference to its presently preferred embodiment, and so used in bottom trawling; however, it will be recognized that certain modifications and changes therein with respect to details may be made without departing from the underlying essentials involved.

Important objects of the present invention are to provide certain trawl door improvements which increase the doors stability in a hydrodynamic sense and provide more reliable and definite positioning of the net in depth :and increased spreading of the net curtains or Wings; and to provide a hydrodynamically efficient door that will also cooperate properly with the said door securing stanchions.

Another important object is an improved trawl door which, by resort to a special multisection construction with separable hollow-core top, bottom and intermediate sections and removable cover panels on each thereof offers certain fabricational and structural advantages and permits interchange of an edge-worn or partially damaged bottom section of a door with a relatively unworn top section of a door, thereby to effectively prolong the useful life of the door and of chafing material at the edges.

A related object in such a hollow-core multisection door construction is the provision of means improving the stability of the door against external pitching moments, and furthermore of insuring positive and reliable action of the door in hugging the bottom along its entire lower edge when applied to bottom trawling.

A durable, light-weight and practical door construction adapted for convenient interchangeability of parts at sea and for construction in relatively large sizes comprise Patented Jan. 24, 1967 still further objects of this invention. Convenience in stowage on board and in launching are also considerations herein.

Among its novel features, a door of this invention comprises top and bottom hollow-core sections having marginally extending flanges and interconnecting reinforcing ribs, portions of which flanges are detachably secured to the respectively adjacent flanges of an intermediate hollow-core section, with top and bottom sections having removable cover plates which serve to contain in one such section bouyancy means and in the other such section ballast means interchangeable with the bouyancy means when the bottom section of a door is interchanged with the top section of a door. Still other features reside in the novel configuration of the door characterized by an :anteriorly concave body plane, with arcuately curved ends and with longitudinally extending slipstream guide vanes mounted on the anterior side to project outwardly therefrom at transversely spaced locations thereon, and extending substantially throughout the major portion of the doors length which vanes cooperate with securing stanchions of the type referred to above, to hold the door stowed immovably when not in use.

These and other features and advantages, together with other and related objects of the invention will become more fully evident from the following description based upon the accompanying drawings.

FIGURE 1 is an exploded isometric view of the illustrated embodiment of the improved door construction including the harnessing rig or bridle for towing the door.

FIGURE 2 is a perspective view of the door rigged for towing and viewed from a posterior forward aspect.

FIGURE 3 is an anterior face view of such a door rigged as described.

FIGURE 4 is a top view of the door, with parts broken away to show certain auxiliary features of construction,

1 posterior side of the door body 12.

such door being shown rigged for towing and for securement to a trawl net.

FIGURE 5 is a sectional view taken on line 55 in FIGURE 4.

FIGURE 6 is a posterior view of the door and of the leading portion of a trawl net secured to the door by the leg lines and lazy lines, in a preferred bottom trawl hookup using a door of this invention.

In describing the illustrative door .and door-connecting arrangements herein, reference is made to the supplemental and amplifying disclosures contained in the abovecited patents and patent applications, concerning matters to which no reference or only passing reference may be made herein. Included in those features is the auxiliary hydrofoil vane assembly 10 which is mounted on the A towing bridle 14, whether comprising the four mutually divergent rigid links 14a, 14b, 14c and 14d or a lesser number, some of which may be flexible, is detachably secured to the anterior side of the door and features a special shackle unit 16 to and through which the towing wrap 18 is secured. Such tow ca'ble embodies an electrical core cable which extends to an electrical connector 20 adapted to engage a complementally formed connector (not shown) in the door body for purposes of transmitting to the trawler electrically detectable trawl net load signals from load sensing units 22 in the door.

Fittings 60 in the forward end of the midsection cover 50 provide a means for securement of the lazy lines L used in trawling equipment (FIGURE 6). Slots 62 in the midsection cover 50 permit the load-sensing unit couplers 22a to project outwardly through the posterior nections sufficient to an understanding of the preferred 3 construction of the door body comprising this invention will be apparent from FIGURE 6.

The present invention is directed primarily to novel features and combinations in the construction of the door body itself including specialized vanes thereon. The door body 12 is of hollow-core, multisection construction which includes the hollow-core upper section 24, a similar lower section 26, and an intermediate section 28, preferably also of hollow-core construction. The door is preferably of generally rectangular proportions with straight top and bottom edges and convexly rounded end edges which are defined by substantially continuous arcuate curves interconnecting the ends of the top and bottom edges. On its anterior face the door is concavely curved or cambered in a longitudinal fore-and-aft sense, whereas on its posterior side it is convexly curved in the same sense and preferably on a somewhat smaller radius. Thereby it is thicker between its ends than at its ends. Such a configuration imparts a certain hydrofoil action to the door comparable to the lift action of an airfoil surface in an airplane, thereby to achieve added spreading action by a pair of such doors connected to the leads of a trawl net. In transverse sections the door is or may be substantially straight at substantially all stations.

In combination with this door configuration as thus far described, the invention also features a plurality of slipstream reaction guide vanes 30 and 32 which extend longitudinally of the door and are mounted on the anterior concave side thereof, spaced at preferably equal distances respectively above and below the longitudinally extending midline of the door, but whether secured to the midsection or the top or bottom section is immaterial. Preferably the vanes 30 and 32 are of hollow construction, triangular in cross section, as seen best in FIGURE 5, and are secured by machine bolts or screws to the anterior paneling of the door, using the securing holes 240' in the latter and securing holes 30a and 32a in the bases of the respective vanes. These guide vanes thus project outwardly from the anterior side and serve the following functions in the usual contemplated application of the invention. In one respect, they serve cooperatively with the door configuration to impart hydrodynamic stabilization, counteracting pitching moment disturbances. A related or ancillary hydrodynamic eifect of these guide vanes is to channel the flow of water longitudinally across the length of the concave anterior face in order to maximize the effectiveness of the concave anterior face in reacting against the slipstream to produce side thrust for purposes of not spreading and to impart to the door a stabilized angle of attack (viz. angularity in relation to the direction of travel). The convexly curved form of the ends of the door in conjunction with its arched body form not only serves hydrodynamic stabilizing and drag-minimizing functions but importantly also cooperates 'with the stanchion bars to help locate and hold the door securely in stowed position. Thus the tips of the door at both ends will project transversely to its general body plane somewhat into the space lying directly between two parallel stanchion bars S1 and S2 against which the anterior face of the door is drawn, so as to nest or cradle between the bars and thereby minimize any tendency for dropping or tilting of either end of the door out of stowed position. In FIGURES 3 and 5 the two cooperating stanchion bars S1 and S2 are shown in broken lines to illustrate the relationship of the bars to the parts of a stowed door. The spacing between vanes 3% and 32 is thus seen to be related primarily to the spacing between stanchion bars.

The hollow-core top section 24 (the bottom section 26 is similar both in construction and form, and for that reason needs no separate description) comprises the peripheral flange 24a extending therearound and having its long sides transversely interconnected by a series of reinforcing ribs 24b located at intervals along the length of such section. Preferably the front side or face of the section 24 comprises paneling 240 which is cast or fabricated and welded integrally with the ribs and flanges in a one-piece construction. Vents or scuppers 24d in the flange, particularly in that portion thereof which lies contiguous to the intermediate door section 28, are provided to permit free flow of water into the cell spaces defined between ribs 2417, thereby to equalize internal compartment pressures with external Water pressure. Preferably the lower-edge flange of the section 24 is flat and seats in uniform contact with the flat upper-edge 28a of the door midsection 28, so that the two sections may be bolted rigidly together by use of the registering bolt holes 40. The similarly formed bottom section 26 is bolted in like manner to the bottom flange 28a of the midsection 28. The midsection is also formed with vent holes 23d and with reinforcing ribs 281) located at intervals along its length and interconnecting the longitudinally extending flange portions 28a and 28a.

Removable flotation material such as rubber sealed molded blocks of resin bonded Wood flakes 46 is placed in one or more cell spaces of the upper door section 24, predominantly aft of the midline thereof. Removable ballast weights, such as rubber sealed lead plates or blocks 58, are placed in one or more cell spaces within the bottom section 26, preferably at a location forward of the vertical midline of the door. The ballasting weights and the buoyancy elements help maintain the door upright in the different stages of a trawling operation and, because of their relative eccentric locations lengthwise of the door, also apply a negative pitch moment urging the nose downwardly for purpose of causing the doors to glide against and along the bottom in the case of bottom trawling.

Cover plates 48, 50 and 52 are secured by bolts or screws to the posterior sides of the respective door sections 24, 28 and 26 in order to complete the door closure and to provide a smooth exterior surface of minimum drag. Such cover plates have vent holes 54 therein which provide controlled flooding of the interior of the door and simultaneous escape of air, to give a very desirable strong momentary additional upright stability to the door during the critical launching period, but then permit internal pressure equalization with the exterior when the door is submerged, and finally permit drainage when the door is lifted from the water.

The door is preferably made primarily of aluminum or aluminum alloy in order to achieve lightness of weight with strength. However, any suitable materials may be used.

Edgings 5'6 of rubber, rubber-like material or other efiicient anti-chafing protective material equivalent thereto are inset in and protectively cover the marginal exberiorly located edges of the three door sections. When the anti-chafe edging strip of a bottom section becomes worn excessively, it is a comparatively simple matter to interchange the bottom section with a top section 24, either of the same door or of the opposing door with which it cooperates, in order to present a relatively unworn edge at the door bottom and thereby to prolong the effective useful life of the edging material. In this regard it will be noted that the interchange of flotation material 46 with ballast material 58 in the top and bottom sections of the same door or of different doors will permit the interchange of sections.

These and other aspects of the invention will be evident to those skilled in the art on the basis of the foregoing description and illustration of the presently preferred embodiment of the invention.

What is claimed is:

1. A bottom trawl door comprising a door body having separate top and bottom edge sections, the latter of which rides upon the bottom, and an intermediate section, said top and bottom sections having substantially identical flanged inner edge portions, and said intermediate section having substantially identical upper and lower flanged edge portions, each of which is matchable with the flanged inner edge portion of both the top and bottom sections; and substantially identical fastening means removably securing the flanged portions of said top and bottom sections to said flanged portions of said intermediate section, whereby the bottom section, with an edge which has become chafed by bottom contact, is interchangeable with the top section which has a relatively unchafed edge.

2. A trawl door according to claim 1, wherein the door body is curved concavely fore and aft on its anterior side and convexly on its posterior side.

3. A trawl door construction comprising a hollow-core, exteriorly vented, multisection door body having a form in its general body plane which is curved concavely fore and aft on its anterior side and convexly on its posterior side, said door body comprising matching hollow-core top and bottom sections and an intermediate hollow-core midsection to which the top and bottom sections are removably secured, whereby the bottom section with a chafed edge of a door is interchangeable with the top section with a relatively unchafed edge of a door, the sections having marginally extending flanges interconnected by reinforcing ribs which extend between anterior and posterior sides of the respective sections, there being a removably mounted cover panel on at least the top and bottom sections, the mutually adjacent flanges of the midsection and adjoining top and bottom sections being detachably bonded together bearing against each other.

4. The trawl door defined in claim 3, wherein flotative material is removably contained in at least one space between ribs, predominantly aft of center, in the upper section, and ballasting weight material is removably contained in at least one space between ribs, predominantly forward of center, in the lower section, and is interchangeable with said flotative material.

5. A bottom trawl door construction comprising separate top and bottom edge sections, and an intermediate section, all removably secured together to define a door body, whereby the bottom section with an edge that has become worn by bottom contact is interchangeable with the top section the edge whereof is unchafed, each of the top and bottom sections being interiorly partitioned to define cell spaces, a weight mass removably received in at least one of the cell spaces of the bottom section, and shiftable to one or more of the cell spaces of the original top section when the latter is interchanged with the original bottom section.

6. A trawl door construction as in claim 5, and flotative means removably received in cell spaces of the top section, and shiftable to cell spaces of the original bottom section when the latter is interchanged with the original top section.

References Cited by the Examiner UNITED STATES PATENTS 1,449,910 3/1923 Oertz 439 2,066,519 l/ 1937 Clark 439 FOREIGN PATENTS 18,499 1895 Great Britain. 210,439 5/ 1924 Great Britain. 305,360 2/ 1929 Great Britain.

SAMUEL KOREN, Primary Examiner.

W. H. CAMP, Assistant Examiner. 

1. A BOTTOM TRAWL DOOR COMPRISING A DOOR BODY HAVING SEPARATE TOP AND BOTTOM EDGE SECTIONS, THE LATTER OF WHICH RIDES UPON THE BOTTOM, AND AN INTERMEDIATE SECTION, SAID TOP AND BOTTOM SECTIONS HAVING SUBSTANTIALLY IDENTICAL FLANGED INNER EDGE PORTIONS, AND SAID INTERMEDIATE SECTION HAVING SUBSTANTIALLY IDENTICAL UPPER AND LOWER FLANGED EDGE PORTIONS, EACH OF WHICH IS MATCHABLE WITH THE FLANGE INNER EDGE PORTION OF BOTH THE TOP AND BOTTOM SECTIONS; AND SUBSTANTIALLY IDENTICAL FASTENING MEANS REMOVABLY SECURING THE FLANGED PORTIONS OF SAID TOP AND BOTTOM SECTIONS TO SAID FLANGED PORTIONS OF SAID INTERMEDIATE SECTION, WHEREBY THE BOTTOM SECTION, WITH AN EDGE WHICH HAS BECOME CHAFED BY BOTTOM CONTACT, IS INTERCHANGEABLE WITH THE TOP SECTION WHICH HAS A RELATIVELY UNCHAFED EDGE. 